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While doing a 200 km trip up north in HEV mode last winter I noticed a few times that the main battery would drop instead of maintaining its charge level. Typically this was at 120 km/h (75 mph) on a trip I assumed was slightly uphill (Kitchener to north of Barrie) This past weekend I had it happen again, this time on a 190 km trip on fairly level terrain (Petrolia to Kitchener). I've checked the elevations, and it turns out that my 200 km trip north actually drops about 80 m, while my trip home last weekend rose 110 m. Either way, the battery bled down despite the fact I was in HEV mode to save EV for city driving. I've never seen the battery at less than 12% before but this time it went all the way down from 70% to 6% (1 white bar on the dash) according to Torque Pro:

I got panicky and dropped the cruise control from 120 km/h to 110 km/h, after which it recovered to 11% by the time I got off the 401 about 25 km later.

Has anyone experienced this before? Anyone have an idea what the car would have done if I hadn't decreased the cruise speed? This was a bit unnerving. I had two passengers in the car, it rained off and on, and there was a headwind; but I still would have expected the ICE to have enough horsepower to maintain speed without killing the traction battery...

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Mine drops when I use SCC and the engine tries to catch up to the speed after slowing down from traffic. Also, while trying to maintain the set speed while going up a slope, it uses EV along with the engine.

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My car is still pretty new, and i havent driven that much without EV yet.
But, i have done it twice,let the EV mode run the battery all the way down, and letting the system it self control what happends.

What i have seen, is the battery will go pretty low the system will go to HEV mode automatickly.
When the battery hits about 8-10%,engine will kick in, and the drive train will run with gas.
At the same time the engine wil charge the battery to 15%, and then it will run EV mode down to about 8% again.
This has been tested at a stable speed of 80kmph/50 mph.

Running in sport mode, seems to keep the battery level high, and run only of gas.

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I've never gone down below 8% SOC and that's been at lower speeds than you were driving, but not on CC Kevin. Usually HEV takes over between 12-15%, and occasionally down to 8% on the Ioniq display.

As I have noted in related thread(s), my experience and no doubt yours too is HEV will only maintain that 8-12-15% SOC range, whereas if I choose Sport mode I can charge to 99% within 45 minutes to an hour driving.

* Were both your Ioniq SOC and Torque Pro SOC displayed and compared? Were they the same SOC or different?

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My car is still pretty new, and i havent driven that much without EV yet.
But, i have done it twice,let the EV mode run the battery all the way down, and letting the system it self control what happends.

What i have seen, is the battery will go pretty low the system will go to HEV mode automatickly.

In this case I put it in HEV mode myself at 70% as I got on the highway to save the battery for city driving at my destination, but the battery drained away anyway over the next 100 km of driving.

Watching the dashboard energy display I often see the car using the electric along with the ICE in HEV mode, sometimes even going fully EV for a downhill, but it always quickly charges the battery back up to maintain the level it was at when I switched to HEV mode. In these few cases the battery just continued to drop even though the ICE was running and connected through the clutch to the wheels (you can tell this because the Motor and ICE rpms are a close match in the Torque Pro display).

It's a head scratcher and I wonder what the car would have done if I didn't reduce speed, but I had passengers with me and didn't want to risk stranding us with the car in a weird state.

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I have seen this a 3-4 times on long journeys going skiing with the family, last time i saw the phenomena there was a very strong headwind, and i could only maintain the charge level when using sports mode manually driving in 5 gear in stead off 6 gear lowering my speed from 120 km/h to 100-110 km/h, and slowly building my charge level from nearly 0 to around 10% over a distance of several hundreds km, that was pretty scary. Car was fully packed with family an gear.

I have just been on my first long trip with this car and found that the battery behaves somewhat strange... My trip was from Denmark to Sweden (Åre) with 200 km highway and 950 km small and big roads, that went up and down all the way. After driving approximately 200 km on gasoline I looked...

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I have seen this a 3-4 times on long journeys going skiing with the family, last time i saw the phenomena there was a very strong headwind, and i could only maintain the charge level when using sports mode manually driving in 5 gear in stead off 6 gear lowering my speed from 120 km/h to 100-110 km/h, and slowly building my charge level from nearly 0 to around 10% over a distance of several hundreds km, that was pretty scary. Car was fully packed with family an gear.

I have just been on my first long trip with this car and found that the battery behaves somewhat strange... My trip was from Denmark to Sweden (Åre) with 200 km highway and 950 km small and big roads, that went up and down all the way. After driving approximately 200 km on gasoline I looked...

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I have seen this a 3-4 times on long journeys going skiing with the family, last time i saw the phenomena there was a very strong headwind, and i could only maintain the charge level when using sports mode manually driving in 5 gear in stead off 6 gear lowering my speed from 120 km/h to 100-110 km/h, and slowly building my charge level from nearly 0 to around 10% over a distance of several hundreds km, that was pretty scary. Car was fully packed with family an gear.

I have just been on my first long trip with this car and found that the battery behaves somewhat strange... My trip was from Denmark to Sweden (Åre) with 200 km highway and 950 km small and big roads, that went up and down all the way. After driving approximately 200 km on gasoline I looked...

Thanks, good thread! My trips north were for snowboarding, but it was just me in the car with the snowboard in the trunk/boot and not many hills, so I was surprised to see the battery dropping in HEV mode. I've done other trips at 130 km/h with the main battery happy to maintain it's charge while driving on gas, so these few occurrences have been odd. I guess it comes down to headwinds and the amount of rain/snow on the roads...

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I have seen this when driving long distance at motorway speeds in HEV/ECO mode.

My guess is that the algorithm deciding when to charge and when to use the portion of the charge encounters an unforeseen, over time unbalanced, situation. The opposite may happen when driving HEV/Sport mode.

It seems there is no exact memory of how the charge was when entering HEV (charge sustaining) mode. It just seems to be, since the algorithm in, over time, balanced situations draw exact the same amount of charge as it puts back. This is because the algorithm is very, very good, but not perfect.

So when algorithm indicates that letting the motor help to save fuel, it expects the situation to soon be that some of the engine energy can be drawn to charge the battery back. If speed or other factors vary normally within a time frame, the two will mostly balance each other out i the same time frame, almost perfect over many time frames.

So I guess the algorithm doesn't exactly know how much has been drawn from or charged to the battery, and hence get no indication it has been failing to maintain charge until charge either reaches maximum or minimum.

This goes with the impression I have that when on long HEV drives in either heavy traffic (speed changes) on motorway, or along hilly roads, curved roads (normal roads, so to speak), I'm usually very impressed on how accurate the battery charge is maintained, almost to the percent. This have earlier led me to think there must be stored figure that it tries to just swing around, but I have not seen such documented or strongly indicated. Now I doubt there is such a figure stored for the time the HEV mod is active.

So I'm back to a very good algorithm, so good that we only see it fail when it encounters exact same ratios between speed an consumption, and almost no braking, over a longer time than possible for such an algorithm to incorporate.

It's well known that Sport mode, in some cases, like constant speed motorway driving, may charge the battery up to a level far higher than it was initially. Sport mode forces the engine to run and be ready for high power at demand. When no sudden, high power is demanded, it has to go to the battery, using he exact same algorithm.

It's a hybrid, it's not designed to ever have 0% battery or an empty fuel tank. They work in concert since an Atkinson cycle engine, while being very efficient, has fairly low torque. So my thought process was that if it was behaving abnormally and drained it's battery all the way down to 0%, it might go into a limp mode or worse; shut down and force me to pull over and stop. Given that I had passengers, I didn't want to deal with either of those situations so I dropped the cruise speed to 110 km/h in the hopes that the battery would recover, which it did. If it ever happens again when I'm alone in the car I'll probably let the experiment run to completion just to see how it ends. (I actually forgot all about Sport Mode, switching to that would have let me continue at 120 km/h and recover the battery as @knutsp pointed out. Maybe it would even have done that itself if I'd let it keep dropping.)

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